1. Field of the Invention
The present apparatus relates to a sheet folding device. More particularly, the subject invention is a crease plow folder that folds cut sheet material or pre-cut continuous web material along a weakened fold-line by first generating a rolled fold around a creasing bar and then changing the direction of the material to buckle the rolled fold and crease it on the weakened fold-line.
2. Description of the Background Art
Traditional xe2x80x9cplow foldersxe2x80x9d have existed for many years and comprise, in general, a cork-screw or helical mechanism that directly generates a fold as the item is transported through the cork-screw mechanism. Usually, the traditional type plow folders produce a crease by forcing the item over a plate as a cork-screw twisting action proceeds.
In particular, U.S. Pat. No. 5,004,452 depicts a device that folds on transverse lines of weakening found in an item to be folded by using an oscillating chute and rotating cams. Focus is drawn to the nature of the exact synchronization scheme utilized in the ""452 invention. The apparatus displayed is not capable of folding individual cut sheets of stock paper.
The device related in U.S. Pat. No. 4,834,696 uses pivoting fold contactors to fold the stock paper as it travels down a pathway. The utilized contactors move in an oscillating wave motion. The ""696 apparatus is not capable of folding a continuous web of paper and the cut stock paper must be spaced some minimum distance apart. As seen below, the subject apparatus of this current disclosure, as opposed to the one in ""696, uses fixed guides, and is capable of folding continuous webs of paper (although not required, usually, the webs are pre-cut before entry into the subject device) or cut sheets of paper with or without spacing and is even capable of folding overlapped individual sheets.
For U.S. Pat. No. 5,449,156, a device is presented that is used to fold continuous web stock paper. The device is not capable of folding individual cut sheets. The disclosed ""156 device stresses the generation of a web tension method, but the folding section description does not show much detail.
The method of U.S. Pat. No. 5,769,773 applies to continuous web pages and does not present a folding scheme. The disclosure mentions standard plow or gate folder technologies.
A continuous web of paper is pulled through the folding device described in U.S. Pat. No. 5,524,421. The ""421 apparatus does not fold cut sheets and unfolded sheets are not transport through it. Additionally, the device requires web tension to crease and square the fold.
Only continuous web materials are folded by the apparatus shown in U.S. Pat. No. 5,755,655. The ""655 device must have the web pulled through to fold and crease the forms. It uses a single point contact to fold 90xc2x0, then the web tension finishes the fold and the output rollers crease the fold.
U.S. Pat. No. 3,799,536 also shows a device that requires continuous web tension to pull the stock paper past the folding plate. This device lacks the capability of being able to fold individual sheets of paper.
Described in U.S. Pat. No. 5,104,366 is a device similar to one noted in ""452 above and is used to fold continuous web sheets along transverse lines. This invention defines a scheme for folding forms with the top sheet of each form in a common orientation independent of the number of pages in the form. It is not capable of folding cut sheets nor can it fold sheets longitudinally.
U.S. Pat. No. 4,624,653 describes a corner laminating apparatus for folding cartons. Included in this device is a pair of opposing spiral roller supports. The spiraled rollers passively force carton sides to fold at desired locations. Conveyor chains with associated lugs transport the cartons through the folding device. Specifically, the ""653 patent describes a device which moves precut blanks of cardboard from a hopper and folds the corners into posts for strength to allow stacking of the gene rated boxes. The system uses a pushing device to drive the cardboard through the folding bars instead of a conveyor. This would not allow overlapped material and would require a space between each box. This system uses rods and rollers to fold the material in an approximately perpendicular manner. Tighter bends are accomplished by using multiple fold sections. This ""653 system folds and creases the material at the same time. In the current subject system the material is rolled and pulled over the crease roller to change its direction which causes the crease. Also, the current subject system is significantly less complicated and applies to individual and relatively thin sheets and not cardboard panels used to produce boxes.
U.S. Pat. No. 4,614,512 relates a sheet folding machine utilized for folding corrugated cardboard into packaging cases. Paired bars or belts are employed to bend opposing sides of the cardboard into folded regions. Specifically, ""512 uses spiral bars to twist the flap over the box forcing the side flaps to fold on a pre-made hinge. This mechanism does not use a bar to hold the flat portion and does not roll the fold, but relies on the xe2x80x9chingexe2x80x9d to locate the fold. This requires that the hinge be significantly weaker than the base material and that the base be held firmly in place. This mechanism uses a vacuum belt to transport the material and therefore requires that the material be non-porous and have few holes. The current subject folder can fold porous materials with large holes. A critical difference between the current subject folder and this folder is that the ""512 folder creases the fold while it is folding whereas the current subject folder rolls the fold first and then the change of direction around the crease roller creases the fold. The ""512 patent notes the disadvantage of folding crossways using the spiral bars. The current subject invention eliminates this problem by first rolling the fold around the crease bar and then changing the direction to buckle the fold and crease it on the perforation.
The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicant""s acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully submitted, however, that none of these patents teaches or renders obvious, singly or when considered in combination, applicant""s claimed invention.
An object of the present invention is to provide a crease plow folder that is capable of folding continuous webs of paper (preferably pre-cut before entry into the subject apparatus) or cut sheets of paper with or without spacing and is even capable of folding overlapped individual sheets.
Another object of the present invention is to furnish a crease plow folder that produces in a desired sheet an initial rolled fold and then a final crease.
A further object of the present invention is to supply a crease plow folder that comprises a non-twist holding and transporting means that delivers a sheet into an initial roll folding means and then a final creasing means.
Still another object of the present invention is to disclose a crease improved plow folder that is capable of folding continuous webs of paper (usually, though not exclusively pre-cut) or cut sheets of paper with or without spacing and is even capable of folding overlapped individual sheets by utilizing a non-twist holding and transporting means that delivers the paper into an initial roll folding means and then a final creasing means.
Yet a further object of the present invention is to describe a sheet folding device that comprises a non-twist sheet holding and transporting means, an initial roll fold generating means, a final crease fold producing means, and sheet alignment tracking means that include a skew-sensor.
Disclosed is a plow folder device engineered to fold sheet stock having a perforated or otherwise weakened fold line. The subject apparatus can be used with cut sheet material or continuous web material. (preferably pre-cut before folding begins). Additionally, it can be setup to transport flat sheet stock without folding, if that is required. The subject invention""s induced fold in a sheet requires some type of weakened fold line. One acceptable method is to employ perforated form stock. Another acceptable method is by adding a perforation or crease generating wheel to the input device.
A portion of the subject plow folding device is designed to accurately hold stock in a fixed orientation without allowing it to twist. The non-twist holding is accomplished by using means comprised of multiple rollers securely attached directly or indirectly to each other and turning at approximately or essentially the same speed, preferably, the same speed. These rollers apply very low forces to the paper at two or multiple positions on the surface. Thus, these rollers transport the paper without applying any significant twisting motion or force. Each sheet is not allowed to twist since that would cause skidding between the sheet and the rollers.
In one embodiment of the subject invention each sheet is fed out of a cutter into the tension rollers. The sheet is still attached to the web at the trailing end. The tension rollers maintain a slight tension on the sheet keeping it flat without allowing it to twist. After the sheet is cut to length it is gently accelerated and transported into the folding section.
An alternative embodiment for the input device is an individual sheet feeder or another type of continuous web to cut sheet device that accurately positions the included fold line. It is noted that if the subject folder were used to fold a continuous web, the tension device would not be required.
The rolling fold portion of the plow folding device uses a generally rectangular bar twisted about its own centerline. This type of construction is relatively easy to produce and allows the folding to be very close to the desired fold line.
The subject folder initially rolls the sheet like a half-tube along the fold line. This action causes the sheet to roll over onto itself without buckling or creasing the fold, thus, allowing the edges of the folded portion to align with the unfolded portion before the creasing operation. By concentrating the folding twist to an area very near the fold line the forces on the folded portion are minimized and the folded portion remains planer with the exception of the rolled portion. To crease the rolled fold the rolled sheet is pulled around a roller driven at the sheet speed. When the sheet begins to change direction around the roller the rolled portions of the sheet moves toward the pitch line of the crease roller in order to maintain a constant sheet speed. This action causes the outer portion of the rolled tube to move in and the inner portion of the roll to move out and forces the sheet to buckle on the weakened fold line. A tapered roller with clearance on the inboard side is utilized to change the sheet direction. This clearance allows the folded sheet to move and align without being captured by the roller.
The transport rollers are supported from one side leaving the system open on an operator side to ease jam removal. In addition, the subject system uses an open design to eliminate paper build up, minimize the transfer of ink and toner, and eliminate the effect of static drag on the paper.
Appropriately positioned sensors to detect sheet twist and skewing. The sensors measure the position of the leading edge of the sheets and if a sheet enters the folder skewed beyond a predetermined maximum amount, the sheet is stopped. This sensor system minimizes the number of damaged sheets and stops the system before it jams. An operator may correct the problem and restart the device quickly.
Conveniently, the subject device can be integrated with many different types of input and output devices because of an input tension roller device, an independent drive system, and a driven output roller system.
Other objects, advantages, and novel features of the present invention will become apparent from the detailed description that follows, when considered in conjunction with the associated drawings.